3.6 pentastar 2020 major problems - Is the newer engine better in 2025 etc.

[Charles 236]

Crankshafts snap due to twisting under load, acceleration forces and such, cams have impact loads on them.

This is the only one I have seen in any 3.6 since the Pentastar came out. This was about a year ago, and it was in an engine that had been "remanufactured" and installed at an independent shop. It is not only possible, but likely, that this one broke because of factors involved in an installation gone bad.

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[ShadowsPapa]

This is the only one I have seen in any 3.6 since the Pentastar came out. This was about a year ago, and it was in an engine that had been "remanufactured" and installed at an independent shop. It is not only possible, but likely, that this one broke because of factors involved in an installation gone bad.

Unlike the block-based cams of the past V8s, where the holes for the cam bearings are line bored and then the bearings put in with a tool, in a straight line, and nothing can change the fit, ever, these rely on the block deck, head surface, head gasket and head bolt torque, among other things, to maintain that perfectly straight line. Anything that deviates from that means that end of the shaft is always under a bit of tension as it spins.
A lot can go wrong.

 

[Stan H]

Crankshafts snap due to twisting under load, acceleration forces and such, cams have impact loads on them.

Could something have been bound up to make it snap also ??@Charles 236

 

[Stan H]

Unlike the block-based cams of the past V8s, where the holes for the cam bearings are line bored and then the bearings put in with a tool, in a straight line, and nothing can change the fit, ever, these rely on the block deck, head surface, head gasket and head bolt torque, among other things, to maintain that perfectly straight line. Anything that deviates from that means that end of the shaft is always under a bit of tension as it spins.
A lot can go wrong.

Truly scary to think of doing that job. All torque specs and sequences would have to be followed to the tee.

 

[ShadowsPapa]

Truly scary to think of doing that job. All torque specs and sequences would have to be followed to the tee.

Absolutely.

Torquing the heads on a cast iron V8 block can actually distort the block a bit! That's why perfectionists building engines use torque plates bolted to the top of the block when boring and doing final honing of the cylinders. The block distorts just a tad - imagine messing up an aluminum engine with incorrect sequences or torque values.

 

[Stan H]

Absolutely.

Torquing the heads on a cast iron V8 block can actually distort the block a bit! That's why perfectionists building engines use torque plates bolted to the top of the block when boring and doing final honing of the cylinders. The block distorts just a tad - imagine messing up an aluminum engine with incorrect sequences or torque values.

Disaster city ,I dont want to imagine

 

[Charles 236]

Could something have been bound up to make it snap also ??@Charles 236

No, if it does bind, the cam would cause the plastic chain guides to break, followed by the chain jumping over the teeth on the phaser. That is, if the engine even started. The starter has what amounts to a "fuse" built into it, and I have seen that fuse fail, causing a no start condition.

 

[ShadowsPapa]

No, if it does bind, the cam would cause the plastic chain guides to break, followed by the chain jumping over the teeth on the phaser. That is, if the engine even started. The starter has what amounts to a "fuse" built into it, and I have seen that fuse fail, causing a no start condition.

Are these non-interference engines?

 

[Charles 236]

According to Chrysler, they are. But I have never seen one actually jump timing. I always verify that the cam will turn freely in the head as far as I can, turning it about 30-40 degrees. If it turns free, fine, if not I will pull the cam and find what is causing it to be tight. I have had an incorrectly machined head that I had to swap out, but only once in the past 15 years.

 

[Stan H]

According to Chrysler, they are. But I have never seen one actually jump timing. I always verify that the cam will turn freely in the head as far as I can, turning it about 30-40 degrees. If it turns free, fine, if not I will pull the cam and find what is causing it to be tight. I have had an incorrectly machined head that I had to swap out, but only once in the past 15 years.

I had a Friend who received a incorrectly milled Cam that was a few degrees off had to send back and they gave him another one. Only one I ever heard of .

 

[Q Tip]

I'll assume you would check the undamaged lobes, and/or the undamaged portions of the damaged lobes, since the hardness of a cam often doesn't go very deep......... thus, once they start, they go fast.

Yes sir an undamaged and squeaky clean surface is necessary for an accurate read. Of course, a read of the damaged area could be beneficial as well. The industrial diamond tip on our tester just needs a good patch say .0625 in dia. I just used the tester on some dowel pins we made this a.m., 1550 degrees for around 1.5hrs, quench in oil yielded 46-47 Rc for raw 4340.

 

[ShadowsPapa]

Yes sir an undamaged and squeaky clean surface is necessary for an accurate read. Of course, a read of the damaged area could be beneficial as well. The industrial diamond tip on our tester just needs a good patch say .0625 in dia. I just used the tester on some dowel pins we made this a.m., 1550 degrees for around 1.5hrs, quench in oil yielded 46-47 Rc for raw 4340.

Yours, sir, is becomming a lost art in this country.
Carry on, carry forward.

 

[Q Tip]

Yours, sir, is becomming a lost art in this country.
Carry on, carry forward.

Thanks for the kind words, machining/toolmaking is a trade i would recommend to anyone. It is actually much easier in our modern era vice the Masters of old techniques and practices. Cnc control means repeatable essentially error less high speed production. You don't even need a calculator....all that Trig is built into the software spitting out complex solutions instantaneously. Im just doing some very simple oven/quench heat treating to save a little time for the customer; serious heat treating is of course a trade and art all its own. If you happen to know any young person looking for a good paying career, get them to call their local community college and get started now!

 

[ShadowsPapa]

Thanks for the kind words, machining/toolmaking is a trade i would recommend to anyone. It is actually much easier in our modern era vice the Masters of old techniques and practices. Cnc control means repeatable essentially error less high speed production. You don't even need a calculator....all that Trig is built into the software spitting out complex solutions instantaneously. Im just doing some very simple oven/quench heat treating to save a little time for the customer; serious heat treating is of course a trade and art all its own. If you happen to know any young person looking for a good paying career, get them to call their local community college and get started now!

I used to work with a guy who went to night classes at the local community college for CNC. DeeZee sent a couple of their people. Sounds like that company is having a heck of a time finding qualified people and people who even want to. I find it fascinating, but then - I was trained on the old ways, a lot of math, you run the machine yourself, no computers, the only automation was setting the table or tool speed (using gears on my cheap chinese lathe)

Bernie said the teacher indicated they'd likely close the class down due to lack of interest. Sad.

I could say my wife is into CNC quilting with the Intelliquilter system on her APQS Millennial long arm quilting machine. That thing fascinates me and how she can manipulate the patterns, tell it areas to skip, and more.

 

[Q Tip]

Yes indeed it's passing me by but I'm nearly done with my career. I'd love to get into additive manufacturing in fact just now heard my old lead man is alive and kicking and has a small kitchen tabletop business 3d printing fishing and boating gear; good for him!

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